Improvement in malleable cast-iron bolts



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N. PHOTO-LITHOGRAPHER WASH NGTON D C .w #tutti tant tattnt WMe-esa die @fitta mw gf `IMIEIRO'VIEIMEINT IN MALLEABLE CAST-IRON BOLTS.

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The Schedule referred to n these LettersPatent and making part of the same.

To all whom 'it mtl/y concern Be it known that I, PINCKNEY FROST, of Springfield,

Windsor county, State of Vermont, have invented certain new and useful Improvements in the Method of Forming Castings for Malleable-Iron Bolts, Screws, Bars, &c. and I do hereby declare. that the following is a full and clear description thereof, reference being had to the accompanying drawings, and to the letters of reference marked thereon.

In the drawings;-

Figures I and III 'are sectional and side views ofvan ordinary bolt.

Figures II and IV are similar views of bolts formed upon my improved plan.

The object of this invention is to'form castings of various kinds, such as bolts, screws, bars,- Stc., intended to be rendered malleable afterwards by the process of annealing, in such a manner that the annealing will be made more thorough, and the article stronger, and, at the same time, lighter, than would be the case if it were cast first in the ordinary manner.

To illustrate this, we will compare an ordinary screwbolt, manufactured in the usual manner,and a similar one, made according to my improved method.

In the first case, the bolt is cast round, afterwards annealed, the threads then being cut upon it.

In Fig. I is 'shown a sectional view of a bolt so formed I previous to the cutting of the threads. In this, it is seen (as is well known to mechanics) that the annealing-process does not affect the metal in the centre of the bolt, but lonly renders malleable an outside shell, of lan average depth of about one-twelfth (T1)of an inc Now, when screw-threads of an ordinary deptlrare cut into a bolt of this kind, they reach nearly entirely through the outside shell of malleable stock, leaving only the more central portion, of .ordinary cast-metal, to withstand whatever1 pressure may be brought against the bolt at this part.`

A In my improved method, however,I form the bolts, before annealing, with longitudinal V- shaped grooves, a., as many as maybe desired', the apexes of which incline towards thev centre of the bolt, and, when the same is annealed afterward, the met-al is affected and rendered malleable by it to an equal depth from the outside-surface; vasjwas the casein the round bolt but,

from the peculiar shape ofthe bolt, in my method the annealed metal reaches through, or nearly through, the centre of the bolt, so that, when the threads are cut around the outside of the same, there is still left a large proportion of annealed metal in the bolt, to strengthen it.

In Fig. II is shown a sectional view of a bolt so formed upon my improved plan.

This principle can be applied to almost any kind of bolt orbar, -nut or screw, and is peculiarly applicable to the small castings used in the building of carriages, agricultural implements, where lightness is desirable,

Aas well as strength.

the central yline of the bolt, as herein described, and for the purpose set forth.

PINOKNEY FROST.

Witnesses:

HORACE W. THOMPSON, HENRY OLossON. 

